Big Tree Registry

Big Tree Champions

Division of Forestry


Measuring a tree

Trees submitted as nominees for the Big Tree Registry must be measured with circumference in inches, and height and crown spread to the nearest foot. The total of these measurements is the points awarded to a particular tree.

Measuring guidelines pdf

Measure a tree at breast height - about 4 1/2 feet about the ground.

1. Circumference

Measure, to the nearest inch, the distance around the tree at a point 4½ feet up from the ground to get the circumference. A flexible tape measure is a good tool to use. When a tree has deep convolutions or indentations, measure without pressing into the indentations.

Hard-to-measure trees:

• Tree with a double stem that forks below 4½ feet above the ground, measure at the narrowest place below the fork.

Measuring a tree with a double stem.

• Tree that has forks at ground level, measure the largest stem at 4½ feet.

Measuring a tree that forks at ground level.

• When the base of a tree is "heaved" (tree roots exposed usually due to the effects of erosion, along with tree movement and growth patterns), the measuring point begins where the root mass ends and the tree trunk begins.

Measuring a tree with a 'heaved' base.

• Tree growing on a slope, measure 4½ feet above the midpoint of the different ground levels.

Measuring a tree on a slope.

2. Height

graphic: measuring height of treeHeight is the hardest measurement to obtain. The most reliable method uses a hand level or hypsometer. If these instruments are unavailable, use a ruler and follow the instructions below.

  1. On a 12-inch ruler, mark the 1-inch and 10-inch lines with tape.
  2. Work in pairs to measure height.
  3. Person A stands at the base of the tree.
  4. Person B, while holding the ruler up in front of their eyes at arm length, moves back until the base of the tree is exactly at 0 inches and the top of the tree is exactly at 10 inches.
  5. Person B sights out from the ruler’s 1-inch mark to a point on the trunk above the base.
  6. Person A marks this spot on the trunk with tape.
  7. Measure the distance from the base of the tree to the 1-inch mark (X) on the tree.
  8. Multiply by 10 to get an approximate height of the tree.

3. Crown spread

  1. Setting a stake directly under the outside edge of the crown farthest from the trunk (A)
  2. Add another stake directly opposite it at the outer edge of the crown on an imaginary line passing through the tree’s center (B)
  3. Rotate 90 degrees and set stakes on outside edges of the crown passing through the center of the tree (C and D)
  4. Measure the distance between points (A) and (B)
  5. Measure the distance between points (C) and (D)
  6. Add the two measurements together and divide the sum by two to find the average crown spread. Average Crown Spread = [(Distance A to B) + (Distance C to D)] / 2
  7. Calculate one-quarter of the crown spread by dividing the average crown spread by four. One-quarter Crown Spread = Average Crown Spread / 4
diagram measuring the crown
One way to measure a tree's crown size - using one transect for the widest part of the crown and one for the narrowest part of the crown.

Awarding points

A champion tree has accumulated the most points based on the measured circumference, height, and crown spread. If two trees of the same species have close scores, co-champions will be crowned if:

Example:

Measurements of tree:
Circumference = 120 inches
Height = 126 feet
Crown Spread = 48 feet

Figuring points:
Circumference = 120
Height = 126
Crown Spread = 48 ÷ 4 = 12
Total points = 120 + 126 + 12 = 258